Optimisation of Deep-Fat Frying of Plantain Chips

cess Pro ing d & o o T F e c f h o Adeyanju et al., J Food Process Technol 2016, 7:5

o DOI: 10.4172/2157-7110.1000584

r Journal of Food

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J Processing & Technology ISSN: 2157-7110

Research Article Open Access Optimisation of Deep-Fat Frying of Plantain Chips (Ipekere) using Response Surface Methodology Adeyanju JA1*, Olajide JO1 and Adedeji AA2 1Department of Food Science and Engineering, Ladoke Akintola University of Technology, Ogbomoso, Oyo State, Nigeria 2Department of Biosystems and Agricultural Engineering, University of Kentucky, Lexington, KY, USA

Abstract Deep-fat frying of plantain chips (ipekere) was investigated with the aim of predicting optimum operating conditions for plantain chips to minimize oil content in order to produce healthy products. The effect of frying temperature and time on moisture content, oil content, breaking force and colour difference of plantain chips was evaluated. Response surface methodology was used to analyze the results of the central composite design of the frying processes for the responses as a result of variation in the levels of frying temperature (150°C-190°C) and frying time (2-4 min). Response surface regression analysis shows that responses were significantly (p<0.05) correlated with frying temperature and time. Regression model was developed for the investigation of the effect of frying temperature and time on the responses. The polynomial regression models were validated with statistical tool whose values of coefficients of determination (R2) were 0.9949, 0.9817, 0.9709 and 0.9966 for moisture content, oil content, breaking force and colour intensity, respectively. The optimum values of moisture content, oil content, breaking force and colour difference were 3.73%, 1.18%, 17.66 N and 65.53 respectively, at frying temperature of 183°C and frying time of 3 minutes. Therefore, frying conditions had a significant effect on the quality attributes of chips produced from plantain.

Keywords: Plantain chips; Deep-fat frying; Regression models; industrial, biological, clinical, social, food, physical and engineering Texture and colour sciences. Optimisation is therefore required to ensure rapid processing while maintaining optimum product quality especially in term of the Introduction quality characteristics. The quality attributes for frying of food materials Plantain (Musa AAB) is one of the most important food crops may include moisture content, oil content, breaking force and colour in the world. It is a major source of carbohydrate, antioxidants and parameters while the process parameters to be optimised include frying minerals like potassium and calcium and caters for the calorific needs of temperature and time. many people in developing countries [1,2]. Nigeria is one of the largest Most published studies on plantain over the years have dealt plantain producing countries in the world with an estimated production primarily with final product quality and physico-chemical changes at 2,722,000 metric tons in 2009 and an average consumption level of in the oil medium during frying [12-15] and none of these reports 190 kg/person/year [3,4]. In spite of its prominence, the country does have particularly optimised frying conditions to obtain fried plantain not feature among plantain exporting nations because it produces more for local consumption than for export. Plantain consumption has chips of acceptable quality attributes. However, there is little or no risen greatly in Nigeria in recent years because of the rapidly increasing published work on statistical approach in RSM during DFF of plantain urbanization and the great demand for easy and convenient foods by chips experiment for obtaining optimum conditions for quality the non-farming urban populations. Besides being the staple for many characteristics of plantain. Therefore, the objective of this work was people in more humid regions, it is a delicacy and flavoured snack for to optimize the DFF conditions with respect to quality attributes like people even in other regions. Plantain chips called Ipekere in south moisture and oil contents, breaking force and colour parameters. western part of Nigeria. It can be produced from green and slightly ripen green plantain with yellow patch, and fried to almost bone dry Materials and Methods with golden yellow colouration. Matured plantain (Musa paradisiacal AAB) fruits harvested at Deep-Fat Frying (DFF) is a multifunctional unit operation of food green stage were procured from a local farm in Ogbomoso, South transformation that can be described as cooking of food by immersion West Nigeria. Plantains were identified in the Department of Crop and in edible oil or fat at a temperature higher than the boiling point of Environmental Protection, LAUTECH, Oyo State, Nigeria. Plantains water [5]. DFF can be considered as a high temperature and a short were washed with clean water, peeled manually and were cut into 2 mm time process which involves both mass transfer, mainly represented by thick slices using a stainless steel knife and a slicer. Refined vegetable oil water loss and oil uptake, and heat transfer [6]. It is one of the major value addition processes for plantain which results in products with a unique flavour-texture combination [7,8]. The primary reason for *Corresponding author: Adeyanju JA, Department of Food Science and Engineering, the popularity of DFF foods may be the characteristics like soft, juicy Ladoke Akintola University of Technology, Ogbomoso, Oyo State, Nigeria, Tel: +234- interior as well as thick and crispy outer crust [9]. Texture, colour and 7087521919; E-mail: [email protected] oil content are the main quality parameters of fried products [10]. Received April 14, 2016; Accepted May 02, 2016; Published May 09, 2016

Response surface methodology (RSM) is a useful technique for Citation: Adeyanju JA, Olajide JO, Adedeji AA (2016) Optimisation of Deep-Fat optimisation studies. This is a collection of mathematical and statistical Frying of Plantain Chips (Ipekere) using Response Surface Methodology. J Food techniques that is useful for modeling and analysis in applications Process Technol 7: 584. doi:10.4172/2157-7110.1000584 where a response is influenced by several factors [11]. RSM is important Copyright: © 2016 Adeyanju JA, et al. This is an open-access article distributed in designing, formulating, developing, and analyzing new scientific under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the studies and products. The most common applications of RSM are in original author and source are credited.

J Food Process Technol ISSN: 2157-7110 JFPT, an open access journal Volume 7 • Issue 5 • 1000584 Citation: Adeyanju JA, Olajide JO, Adedeji AA (2016) Optimisation of Deep-Fat Frying of Plantain Chips (Ipekere) using Response Surface Methodology. J Food Process Technol 7: 584. doi:10.4172/2157-7110.1000584

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(Devon King’s®) obtained from Ace Supermarket, Ogbomoso was used Testometric AX, Rochdale, Lancashire, England) equipped with a 50 as the frying medium in the deep-fat frying process. kN load cell. Fried plantain chips of uniform sizes were selected and then placed on a metal support with jaws at a distance of about 25 mm. Frying Operation They were pressed in the middle with a cylindrical flat end plunger Frying was carried out in a deep-fat fryer (model MC-DF 1031, Cool (70 mm diameter) at a speed of 2.5 mm/min. The measurement was Touch deep fryer, General Electric, Hong Kong, China) adapted with recorded by a computer connected directly to the equipment. The a PID temperature controller to maintain the set frying temperature breaking force (N) interpreted as crispness was obtained as the peak within ±1°C. The fryer was filled with 2.5 L of oil and equipped with a 2 force from the force-deformation curve [17]. kW electric heater. Plantain slices to oil ratio was kept at 1:10 was used. Colour: Colour parameters lightness (L*), redness (a*) and The oil was preheated prior to frying and discarded after 2 h. Before yellowness (b*) were measured using a colorimeter (Colour Tec-PCM, each frying test, the oil level was checked and replenished as required. Hunterdon, NJ) as described by Krokida et al. [18]. The instrument Samples were fried at temperatures 150°C, 160°C, 170°C, 180°C and was standardized and the samples were placed in the sample holder. 190ºC, for 120, 150, 180, 210 and 240 seconds. After frying, excess Samples were scanned at different locations to determine (L*, a* and oil was removed by shaking the baskets manually and the chips were b*) parameters. Colour difference (ΔE) was calculated according to the placed on a rack to cool. Samples were stored in sealed, low density equation: polyethylene bags and kept at room temperature until analyses were performed. Colour difference (Hunter ∆=E) [(LL−−− )2 + ( aa )2 + ( bb )2 ] 1/2 Experimental Design ref ref ref (1) Where L , a and b were the L, a and b values of fresh plantain Central composite of RSM for a two-variable experimental design ref ref ref slices which were used as references. was employed [11]. The independent factors considered were frying temperature (X1: 150°C, 160°C, 170°C, 180°C and 190°C) and time (X2: Statistical analysis 2, 2.5, 3.0, 3.5 and 4.0 min) while the dependent factors were moisture content, oil content, breaking force and colour difference (∆E) (Table 1). All data were analyzed using the Design-Expert Version 6.0.8 (State-ease software). Regression analysis and analysis of variance Quality characteristics determination (ANOVA) were conducted by fitting the equation to the experimental data to determine the regression coefficients and statistical significance Moisture content: Five gram was weighed into a pre-weighed of model terms. The significance of the model terms was assessed by moisture dish. The dish plus sample taken was transferred into the oven F-ratio at a probability p<0.05. Model adequacies were determined pre-set at 105°C to dry to a constant weight for 24 hours overnight. At using model analysis, lack of fit test and coefficient of determination the end of the 24 hours, the dish plus sample was removed from the (R2). oven and transferred to desiccator, cooled for 30 minutes and weighed [16]. Optimisation procedure Oil content: Oil content was determined according to method Numerical optimisation was performed using Design Expert described by AOAC [16] using soxhlet extraction. Fried samples were software V 6.0.8. Multiple responses were optimised simultaneously ground using a grinder. Five gram of sample was weighed into thimbles through the use of a desirability function that combines all the for fat extraction in a solvent extractor using petroleum ether. Fat responses into one measurement. The method finds operating content was determined as the ratio of the mass of extracted fat and dry conditions (combination of independent variables) that maximizes matter of the sample. the desirability function. The constraints were set to get the value of Breaking force: The texture (breaking force) of the chips a variable for an optimum response (a minimum and maximum level was determined using a universal testing machine (model M500, must be provided for each variable included). The optimisation of the

Run Coded Actual Responses

x1 x2 X1 X2 MC (%) OC (%) BF (N) ∆E 1 -1.0 -1.0 190 4 3.67 1.22 21.41 34.56 2 1.0 -1.0 170 4 3.69 1.20 15.97 55.89

3 -1.0 1.0 180 3 3.77 1.20 15.75 51.39 4 1.0 1.0 170 3.5 3.5 1.19 17.78 52.64 5 0.0 1.414 190 2 3.76 1.22 24.90 56.80 6 0.0 -1.414 150 4 4.37 1.14 24.11 66.99 7 1.414 0.0 160 3.5 4.32 1.18 18.59 60.24 8 -1.414 0.0 170 3 3.69 1.20 15.97 55.89 9 0.0 0.0 180 2.5 3.91 1.21 18.88 54.55 10 0.0 0.0 190 3 3.86 1.20 15.67 47.73 11 0.0 0.0 170 3 4.06 1.19 22.40 49.19 12 0.0 0.0 170 2 4.19 1.19 17.78 52.64 13 0.0 0.0 170 3 4.02 1.22 23.01 56.42 Where: X1 = Frying temperature (oC), X2 = Frying time (min), MC = Moisture content, OC = Oil content, BF = Breaking force and ∆E = Colour difference Table 1: Experimental design arrangement and responses.

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DFF process was aimed at finding the levels of frying temperature and Equation 2 indicates that at linear level, temperature and time time, which could minimize the moisture content, oil content, breaking had negative effect on the moisture content. At quadratic level, all the force and moderate colour. variables had positive effect on the moisture content, while interaction between temperature and time had negative effect. Effect of moisture Results and Discussion content with frying temperature and time are shown in Figure 1. Significant interaction suggests that the level of one of the interaction Estimation of the model parameters for plantain chips variables can be increased while that of other decreased for constant (Ipekere) value of the response. Shyu and Hwang [19] reported that the unbound The experimental data and their corresponding responses are water in the fried food can be rapidly removed when the oil temperature shown in Table 1. Multiple regression and correlation analysis are reaches the boiling point of water. The effects of frying temperature used as tools for assessment of the effects of two or more independent and time were significant (p<0.05) on the moisture content. Response variables on the dependent variables. The coefficients of determination plot (Figure 1) revealed that the rate of moisture loss in plantain chips (R2) for moisture content, oil content, breaking force and colour are increased by increasing the frying temperature and time. The moisture 0.9647, 0.9844, 0.9303 and 0.9773, respectively. These values are quite changes during frying showed the typical progressive decrease with high for response surfaces and indicated that the fitted quadratic models increasing frying time. The result obtained was similar to the findings accounted for more than 95% of the variance in the experimental of [20,21] on French fries and chicken meat respectively. 22 data, which were found to be highly significant. The only regression MC =−33.51 0.31XX − 2.11 +− 8.91E 004X + 0.25X −− 2.73E 003X X (2) coefficients significant at 95% levels according to p-values were selected 1 2 1 2 12 22 OC = 1 .01+− 5.87E 003X − 0.24X − 2.32E − 005X +− 9.48E 003X + 9.98E − 004X X for developing the models (Table 2). 1 2 1 2 1 2 (3) 22 Adequacy test of the models for plantain chips = 322.02 – 2.82X− 34.94X +− 7.79E 003X + 4.87X − 0.02X X BF 1 2 1 2 1 2 (4) The fitted models were tested for adequacy and consistency ∆=E −+70.18 0.78X + 64.40X − 0.39X X (5) by analysis of variance (ANOVA). The results from the statistical 1 2 1 2 analysis revealed that the F-value for moisture content (38.21), oil Oil content content (88.19), breaking force (18.69) and colour difference (129.08) As shown in Equation 3, at linear level, temperature and time were significant at the 95% confidence level. Analysis of variance had negative effect on the oil content. At quadratic level, temperature for response surface quadratic models of plantain chips is shown in had negative effect and time had positive effect, while the interaction Table 2. The empirical models obtained for the quality characteristics between temperature and time had positive effect on the oil content. of plantain chips are stated as equations 1 to 4. Quadratic model was Significant interaction suggests that the level of one of the interaction found to satisfactorily explain the relationship for moisture content, oil variables can be increased while that of other decreased for constant content and breaking force while 2FI model was used to represent the value of the response. The relationship of oil content with frying relationship between colours of ipekere as affected by frying conditions. temperature and time are shown in Figure 2. The increased oil The model satisfied lack of fit test. Significant model terms at p<0.05 absorption during deep frying of plantain may be accredited to were frying temperature (X ), frying time (X ), second order of frying 1 2 changes in porosity and molecular size redistribution. The oil content temperature and time (X 2, X 2) and interaction of frying temperature 1 2 in fried products needs to be optimised because it affects the texture and time (X X ). Therefore, the model is appropriate for predicting 1 2 and appearance of the chips [22]. The final oil content of the chips moisture content, oil content, breaking force and colour as influenced is affected by the plantain’s physicochemical characteristics and the by frying temperature and time. processing conditions. Moreover, oil content in a product can depend Effect of Variables on the Responses on the frying temperature, time as well as moisture content [23-25]. The result obtained was similar to the findings of [26] who reported Moisture content increase in fat content at longer frying time. Breaking force Responses Sources of DF Sum of Mean Breaking force was used to represent the crispness of fried plantain Variation Squares Squares F-value R2 chips. Frying temperature and time had negative linear effect on the MC Regression 5 0.650 0.130 38.211 0.9647 crispness of the chips. At quadratic level, temperature had negative Residual 7 0.023 0.003 effect and time had a significant positive effect, while interaction Total 12 0.674 between temperature and time had negative effect on the crispness. OC Regression 5 0.005 0.001 88.194 0.9844 The interaction effect of temperature and time on crispness is Residual 7 9.01E-05 1.29E-05 shown in Figure 3. As shown in Equation 4, at the two independent Total 12 0.005 variables, second order derivatives and interactions between the BF Regression 5 125.966 25.193 18.695 0.9303 Residual 7 9.433 1.347 variables are significant. Results showed that the effects of temperature Total 12 135.399 were significant (p<0.05) on the crispness of the plantain chips. As ΔE Regression 5 660.2538 220.084 129.08 0.9773 temperature of frying increases, the rate of moisture removal becomes Residual 7 675.599 faster, thus favoring the frying process. The breaking force of the chips Total 12 0.650 0.130 38.211 decreases as frying temperature and time increases. Crispness of chips

Where: MC = Moisture content, OC = Oil content, BF = Breaking force and ∆E = is a vital measure that determines the consumers’ acceptance [27]. It is Colour difference the most important textural attribute which denotes freshness and high Table 2: Analysis of variance for the responses. quality. The peak compression force increased with increasing frying

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MC X = A: Temperature Y = B: Time

4 .4 6 9 2 5

4 .2 7 6 4 2

4 .0 8 3 5 9

3 .8 9 0 7 5

C M

3 .6 9 7 9 2

4 .0 0 1 9 0 .0 0 3 .5 0 1 8 0 .0 0 3 .0 0 1 7 0 .0 0

B : T i m e 2 .5 0 1 6 0 .0 0 A : T e m p e r a tu r e 2 .0 0 1 5 0 .0 0

Figure 1: Response surface plot showing the effect of frying temperature and time on moisture content of plantain chip. Figure 1: Response surface plot showing the effect of frying temperature and time on moisture content of plantain chip.

OC X = A: Temperature Y = B: Time

1 .2 2 7 4 4

1 .2 0 6 4 4

1 .1 8 5 4 5

1 .1 6 4 4 5

C O

1 .1 4 3 4 6

4 .0 0 1 9 0 .0 0 3 .5 0 1 8 0 .0 0 3 .0 0 1 7 0 .0 0

B : T i m e 2 .5 0 1 6 0 .0 0 A : T e m p e r a tu r e 2 .0 0 1 5 0 .0 0

Figure 2: Response surface plot showing the effect of frying temperature and time on oil content of plantain chip. Figure 2: Response surface plot showing the effect of frying temperature and time on oil content of plantain chip.

BF X = A: Temperature Y = B: Time

2 9 .4 0 0 6

2 6 .0 3 1 5

2 2 .6 6 2 4

1 9 .2 9 3 3

F B

1 5 .9 2 4 2

4 .0 0 1 9 0 .0 0 3 .5 0 1 8 0 .0 0 3 .0 0 1 7 0 .0 0

B : T i m e 2 .5 0 1 6 0 .0 0 A : T e m p e r a tu r e 2 .0 0 1 5 0 .0 0

Figure 3: Response surface plot showing the effect of frying temperature and time on breaking force of plantain chip. Figure 3: Response surface plot showing the effect of frying temperature and time on breakingforce of plantain chip.

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Colour X = A: Temperature Y = B: Time

6 7 .3 8 4 7

5 9 .3 8 1 4

5 1 .3 7 8 1

4 3 .3 7 4 8 r u o l

o 3 5 .3 7 1 4 C

4 .0 0 1 9 0 .0 0 3 .5 0 1 8 0 .0 0 3 .0 0 1 7 0 .0 0

B : T i m e 2 .5 0 1 6 0 .0 0 A : T e m p e r a tu r e 2 .0 0 1 5 0 .0 0

FigFigureure 4: R4:e sResponseponse sur fsurfaceace plot plotsho wshowinging the etheffe ceffectt of fr yofin gfrying temp temperatureerature and t iandme otimen co lonou rcolour intens differenceity of plant aofin plantainchip. chip. conditions or when the initial plantain moisture content was lower. The The optimum values for moisture content, oil content, breaking result obtained was in agreement with the findings that the hardness of force and colour difference from the surface plot was 3.73%, 1.18%, fried chickpea flour-based snack increased at lower moisture content of 17.66 N and 65.53, respectively. Therefore, temperature and time the pre-fried product [28]. were determined to have significant effect on the quality attributes of plantain chips. Thus, the optimized frying conditions were able to Colour difference produce high quality plantain chips. The effect of interaction of temperature and time on colour References intensity is shown in Figure 4. As reflected in Equation 5, at linear level, 1. Kanazawa K, Sakakibara H (2000) High content of dopamine, a strong temperature had negative effect; time had a significant positive effect on antioxidant, in Cavendish banana. J Agric Food Chem 48: 844-848. the colour difference. At quadratic level, temperature had positive effect and time had negative effect, while interaction between temperature 2. Mohapatra D, Mishra S, Sutar N (2010) Plantain and its byproduct utilization: An overview. J Sci Ind Res 69: 323-329. and time had negative effect on the colour. The colour intensity of plantain chips decreased progressively as the frying temperature and 3. FAO (2011) Production, commodity by country; FAOSTAT Data. Food and Agriculture Organisation of the United Nations, Rome. time increased (Figure 4). This indicates that higher ∆E values will lead to lower colour quality on the surface of plantain chips. It was 4. FAO (2013) Food and Agriculture Organization of the United Nations. Crop yield. observed that an increase of temperature led to a significant formation of brown products. The modification in fried plantain colour is mainly 5. Farkas BE, Hubbard LJ (2000) Analysis of heat transfer during immersion due to the effect of temperature on heat-sensitive compounds such as frying. Dry Technol 18: 1269-1285. carbohydrates, proteins and vitamins, which cause colour degradation 6. Vitrac O, Dufour D, Trystram G, Raoult-Wack A (2002) Characterization of heat during drying process. The formation of brown compounds in plantain and mass transfer during deep-fat frying and its effect on cassava chip quality. J Food Eng 53: 161-176. may be related to both enzymatic and essentially non-enzymatic (maillard reaction) reactions [29]. This result is similar to the report 7. Mellema M (2003) Mechanism and reduction of fat uptake in deep-fat fried of [30] that colour changes also indicated more mallard reaction with foods. Tr Food Sci Technol 14: 364-373. frying time which utilized the abundant reducing sugars in plantain. 8. Pedreschi F (2012) Frying of potatoes: Physical, chemical and microstructural changes. Dry Technol 30: 707-725.

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J Food Process Technol ISSN: 2157-7110 JFPT, an open access journal Volume 7 • Issue 5 • 1000584